Re: 32KB Tuples

Patrick Welche wrote:

> On Tue, Jun 06, 2000 at 06:42:08PM +0200, Jurgen Defurne wrote:
> > A 'tuple' is an element of a set. A set is also called a table. When you do N
> > insertions on a table, then you get a table/set of N tuples. When you
> > query a table/set, then your result is also a set. This set can consist of
> > 0 to N tuples.
> >
> > To put it in another perspective :
> > tuple     <-> row    <-> record
> > relation <-> table  <-> 'file'
> >
> > Since SQL manipulates sets, giving other sets, your first thought, is also
> > correct.
> >
> > The other part of you question deals with projection, which means that
> > you only take some fields. However, if you do a query like
> > SELECT * FROM table WHERE select condition
> > OR
> > SELECT field1, field2 FROM table WHERE select condition
> >
> > both will return the same number of tuples, but in the second set, the
> > tuples will consist of only two fields.
>
> So where is the 8K or 32K limit? For the
> SELECT * FROM table WHERE select condition
> or the
> SELECT field1, field2 FROM table WHERE select condition
> case?
>
> Cheers,
>
> Patrick

The limit is in the length of the tuple of a base table. Counting the lengths
of all fields in a tuple together may not be larger than 8192 bytes
(or 32768 bytes if you changed your configuration).

Suppose you have a tuple with 1 text field, then you will not be able to
store more than 8192 bytes in the field. If you have two text fields, then
if field 1 contains N bytes, then field 2 can only contain 8192 - N bytes.

The limits are not in the SQL statements, but in the physical files which
are used to create the tables.

Jurgen Defurne
defurnj@glo.be